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Old 17th January 2008, 11:52 AM   #11
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Also note that the lowest impedance you can use is 8 ohms in bridge as each half effectively sees 4 ohms.
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Old 27th February 2012, 02:25 AM   #12
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Actually I was looking for someone that already tested the config
For the simplest method, go for Project 14 at ESP

Bridging Adapter For Power Amps

i've being using this method for my LM1875 DIY amp ... and it works nicely ....

Good luck
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Old 3rd March 2012, 05:59 AM   #13
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could you share to us your configuration?? thanks
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Old 6th March 2012, 11:13 PM   #14
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I know you have already got some 1875s, and by all means test them in bridged mode to see if it is alright, but they are completely the wrong chip to to use for any sort of sub, especially bridged. They simply don't have the current capability. You save yourself 3 by using them, but a single 3886 will outdo what they can do in a bridged configuration. You might just about get away with what you want in a simple parallel setup, where the current is halved for each, but I would not set too much store by just what you have to hand in front of you.
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Old 11th March 2012, 04:01 AM   #15
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What is the speaker load?
If 8 ohms, one pair of 2-chip parallel LM1875's might do for bridging.
If 4 ohms, one pair of 3-chip parallel LM3886's might do for bridging.

Paralleled LM1875 into a 4 ohm load = 55 watts. Solo LM3886 into a 4 ohm load = ~45 watts due to on-chip limiter activation.
If you want more power than these, make BPA300 with 6 LM3886 and a small op-amp for phase inverter, and you can add a Stereo buffer (at subwoofer amp input) so you can downmix to mono without smashing the imaging of your main speakers.
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Old 11th March 2012, 04:13 AM   #16
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Or the answer. . .
You may be able to sub LM1875 for TDA2030 and you may be able to sub MJL21193/MJL21194 for BD250/BD249. Maybe. But, with the sturdy helpers, the bridged LM1875 now pushes the 4 ohm woofer.
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Old 11th March 2012, 06:44 AM   #17
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Originally Posted by ChristianThomas View Post
they are completely the wrong chip to to use for any sort of sub, especially bridged.
It depends. For a top notch subwoofer that is supposed to deliver the lowest audible notes at original concert listening levels, any chip amp is the wrong choice.

If you choose the woofer and enclosure wisely, you can end up with a surprisingly decent sub for civilised listening levels even with an LM1875.

And in this case, where the subs only needs to improve the performance of PC speakers with a probably rather small woofer, an LM1875 is likely to be more than sufficient, whether bridged or not.
If you've always done it like that, then it's probably wrong. (Henry Ford)
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